Drawing Polygons
To draw a polygon, activate the polygon tool and click on the document at the place you'd like the polygon to start.
Each time you click on the document, you will add another point to the polygon. To finish creating a polygon, either click on the first point or double-click to place a final point.

Hitting Backspace or Delete while creating a polygon will remove the last point that added.

Hitting ESC while creating a polygon cancels the polygon.

Double-click on an existing polygon border to add another point.